My friend's old Kawie 650 SX did that because the ski sat around then he got it running. It destroyed the cases, cylinder, bed plate, starter, reed cage, crank, ect..
Well I thought it was pretty cool until the next year my X2 did the same thing from having too much water in the gas. Thos water traps Kawasaki use are a joke. I remove them from now on. Well my ski kept running on one cylinder. I guess I got lucky because my starter, intake manifold, and reed cage didn't get busted up.
When an engine blows liek that, it really blows a hole in your wallet! $$$$